The BT 136 is a bidirectional thyristor, commonly referred to as a triac, designed for controlling AC power. It is capable of switching and regulating current in both directions, making it an essential component in various AC power control applications. The BT 136 is widely used in light dimmers, motor speed controllers, heating systems, and other devices requiring efficient AC power management.
Its ability to handle high voltages and currents, combined with its compact size, makes it a popular choice for both industrial and consumer electronics.
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This circuit appears to be a transistor-based switching or amplification system powered by a 12v battery, with an AC supply possibly for signal input or additional power. It includes filtering through ceramic capacitors and uses resistors for biasing the transistors. The presence of both PNP and NPN transistors suggests a push-pull configuration or a form of signal modulation.
This circuit appears to be a power supply circuit with a transformer connected to a 12V battery for voltage step-up or step-down. It includes a rectification stage with a 1N4007 diode, smoothing with an electrolytic capacitor, and regulation using a Zener diode. Additionally, there are inductors for filtering and a BT139 600 triac for controlling AC power, possibly for dimming or switching applications.
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This circuit features a Nano 33 BLE microcontroller interfaced with a TM1637 4-digit 7-segment display for information output, powered by a 3.7V battery managed by a TP4056 charging module. The microcontroller communicates with the display to present data, while the TP4056 ensures the battery is charged safely and provides power to the system.
Below are the key technical details of the BT 136 triac:
Parameter
Value
Maximum Repetitive Voltage (VDRM)
600V
Maximum RMS On-State Current (IT(RMS))
4A
Peak Non-Repetitive Surge Current (ITSM)
25A (for 20ms half-sine wave)
Gate Trigger Voltage (VGT)
1.5V (typical)
Gate Trigger Current (IGT)
5mA (typical)
Holding Current (IH)
2mA (typical)
Operating Temperature Range
-40°C to +125°C
Package Type
TO-220
Pin Configuration
The BT 136 has three pins, as described in the table below:
Pin Number
Name
Description
1
MT1 (Main Terminal 1)
One of the main current-carrying terminals.
2
MT2 (Main Terminal 2)
The other main current-carrying terminal.
3
Gate
Used to trigger the triac into conduction.
Usage Instructions
How to Use the BT 136 in a Circuit
Basic Circuit Design:
Connect the AC load (e.g., a lamp or motor) in series with the BT 136's MT2 terminal.
MT1 is connected to the neutral or return line of the AC supply.
The gate terminal is connected to a triggering circuit, such as a microcontroller or a resistor-diode network.
Gate Triggering:
To turn the triac on, apply a small current to the gate terminal. This current can be supplied by a microcontroller, such as an Arduino, or a simple RC network.
Once triggered, the triac will remain on until the current through MT1 and MT2 drops below the holding current (IH).
Snubber Circuit:
For inductive loads (e.g., motors), include a snubber circuit (a resistor and capacitor in series) across the triac to prevent voltage spikes and ensure reliable operation.
Important Considerations
Heat Dissipation: The BT 136 can generate significant heat during operation. Use a heatsink if the current exceeds 2A to prevent overheating.
Isolation: Ensure proper electrical isolation between the gate control circuit and the AC load to avoid damage to sensitive components.
Gate Resistor: Use a resistor (typically 330Ω to 1kΩ) in series with the gate to limit the current and protect the gate terminal.
Example: Controlling a Lamp with Arduino UNO
Below is an example of how to use the BT 136 to control an AC lamp with an Arduino UNO:
// Example: Controlling an AC lamp using BT 136 and Arduino UNO
// Note: Use an optocoupler for isolation between Arduino and the AC circuit.
const int gatePin = 9; // Pin connected to the gate of the BT 136
void setup() {
pinMode(gatePin, OUTPUT); // Set the gate pin as an output
}
void loop() {
digitalWrite(gatePin, HIGH); // Trigger the triac to turn on the lamp
delay(1000); // Keep the lamp on for 1 second
digitalWrite(gatePin, LOW); // Turn off the triac (lamp will turn off
// when AC current crosses zero)
delay(1000); // Wait for 1 second before turning it on again
}
Note: This example assumes the use of an optocoupler (e.g., MOC3021) to safely interface the Arduino with the BT 136. Directly connecting the Arduino to the gate of the triac is not recommended due to the high voltages involved.
Troubleshooting and FAQs
Common Issues
Triac Does Not Turn On:
Check the gate trigger voltage and current. Ensure the gate resistor value is appropriate.
Verify that the triggering circuit is functioning correctly.
Triac Turns On but Does Not Turn Off:
Ensure the load current drops below the holding current (IH) to allow the triac to turn off.
For inductive loads, verify that a snubber circuit is in place.
Overheating:
Check the current through the triac. If it exceeds the rated RMS current, use a heatsink.
Ensure proper ventilation around the component.
Gate Damage:
Verify that the gate current does not exceed the maximum rating. Use a resistor to limit the current.
FAQs
Q1: Can the BT 136 be used for DC applications?
No, the BT 136 is designed for AC applications. It relies on the zero-crossing of the AC waveform to turn off.
Q2: What is the maximum load the BT 136 can handle?
The BT 136 can handle up to 4A RMS current. For higher currents, consider using a triac with a higher current rating.
Q3: Do I need an optocoupler to use the BT 136 with a microcontroller?
Yes, it is highly recommended to use an optocoupler (e.g., MOC3021) to isolate the low-voltage microcontroller from the high-voltage AC circuit.
Q4: Can I use the BT 136 without a heatsink?
Yes, but only if the current through the triac is below 2A. For higher currents, a heatsink is necessary to prevent overheating.
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